Dynamic Contact Angle on PTFE Surface by Aqueous Surfactants Solution in Absence and Presence of Electrolytes

Abstract

This study presents the experimental results on dynamic contact angles of pure surfactants and surfactants with electrolyte solutions on PTFE (Teflon) surface. Dynamic advancing (qA) and receding (qR) contact angles measurements by the Wilhelmy plate technique were carried out for aqueous solution of three different surfactants TritonX–100 (TX–100), sodium dodecylbenzene sulfonate (SDBS), and cetyltrimethylammonium bromide (CTAB). The same measurements in presence of different electrolytes NaCl, Na2SO4, and CaCl2 for ionic surfactants (SDBS and CTAB) were also carried out to see the change in contact angle and wetting behavior. The presences of electrolytes change the advancing contact angle as well as wetting properties of hydrophobic solid surface significantly even at very low surfactant concentration. Counter ion valency of the electrolyte is more important in reducing advancing contact angle on hydrophobic PTFE surface at very low concentration of ionic surfactants from CMC. Pure surfactants and ionic surfactants in presence of electrolytes show a linear relationship between the adhesional tension and surface tension at air – water interface with different slope and intercept.